Damper unit for a ventilation system

ABSTRACT

A damper unit for ventilating systems and comprising a housing having two internal ducts or passages for fresh air and return air, respectively, and an internal by-pass between the ducts. The ducts are parallel at the outer end of the housing and concentric at the inner end thereof. One of the internal ducts is defined by an inclined, tubular partition wall which at its outer end merges with the housing wall and with a central partition between the parallel outer duct ends. A pivotal damper has a first end position in which it obturates the by-pass which is provided in the central partition, and a second end position in which it obturates the outer ends of both ducts and opens the by-pass to provide full recirculation of spent room air. In intermediate positions the damper provides for partial recirculation.

United States Patent [1 1 Holt et al.

[451 Feb. 12, 1974 DAMPER UNIT FOR A VENTILATION SYSTEM [73] Assignee: Nordisk Ventilator Co. A/S,

Naestved, Denmark [22] Filed: July 5, 1972 [21] Appl. NO.: 268,955

[30] Foreign Application Priority Data July 6, 1971 Denmark 3323/71 Sept. 6, 1971 Denmark 4371/71 [52] US. Cl 98/33 A, 98/41, 98/62 [51] Int. Cl F24f 7/06 [58] Field of Search 98/32, 33 R, 33 A, 41, 62; 137/610, 625.44, 625.45

3,557,681 l/l97l Kristiansen 98/33 R Primary Examiner-William F. ODea Assistant ExaminerPeter D. Ferguson Attorney, Agent, or FirmSughrue, Rothwell, Mion,

Zinn and Macpeak A damper unit for ventilating systems and comprising a housing having two internal ducts or passages for fresh air and return air, respectively, and an internal by-pass between the ducts. The ducts are parallel at the outer end of the housing and concentric at the inner end thereof. One of the internal ducts is defined by an inclined, tubular partition wall which at its outer end merges with the housing wall and with a central partition between the parallel outer duct ends. A pivotal damper has a first end position in which it obturates the by-pass which is provided in the central partition, and a second end position in which it obturates the outer ends of both ducts and opens the by-pass to provide full recirculation of spent room air. In intermediate positions the damper provides for partial recirculation.

8 Claims, 5 Drawing Figures PATENTED FEB 1 2l974 SHEEI 1 BF 5 PATENTEDFEB 1 21974 I SHEH 3 0F 5 PATENTEUFEBmQM SHEET '4 BF 5 PATENTED FEB! 2I974 SHEH 5 BF 5 DAMPER UNIT FOR A VENTILATION SYSTEM BACKGROUND OF THE INVENTION The present invention relates to a damper unit for a ventilation system, comprising a housing that has a tubular outer wall and at one end thereof two concentric or essentially concentric apertures for connection to a central duct and to a surrounding annular duct in the ventilation system, respectively. One of said ducts serves to convey fresh air to the ventilated room or rooms, while the other duct conveys return or spent air from the room. At its opposite or outer end, the housing is provided with apertures for drawing in fresh air and for exhausting spent air, respectively, and between said ends the housing is provided with damper means for simultaneously varying the cross-sectional areas of the flow passages for fresh air and return air and of a by-pass or circulation passage connecting the fresh air and return air passages.

A unit of this type, known from Danish patent specification No. 1 15,495, has two convex or arched damper plates which may pivot through an aperture in the wall ofa central duct in the unit that forms a continuation of the connected central ventilating duct. The plates are pivotal between one end position in which they abut against the wall, and a second extreme posi tion in which they extend obliquely across and close both the central duct and a surrounding annular duct in continuation of the second ventilation duct while, at the same time, they open the aperture between the two ducts of the unit. In the first extreme position, the supply of fresh air is at its maximum and the entire volume of return air from the ventilated room is exhausted, while in the second end position of the damper plates, a 100 recirculation of the room air is effected. In intermediate positions of the damper plates, a partial recirculation takes place so that the spent room air is mixed with a certain volume of fresh air,'the magnitude of which depends upon the adjustment of the damper, while a corresponding volume of spent air is discharged. In actual practice, the damper unit described has been found to be rather sensitive to depositions of dust on the damper plates since the pivot axis of each plate will of necessity be located rather much offset in relation to the mass or area centre of the plate, for which reason the plates are normally balanced with the aid of counterweights so as to limit the requisite adjusting force. As the surface area of the counterweight is considerably smaller than that of the damper plates, deposited dust, even if the deposition takes place uniformly on the surface, produces an unbalance that may render the adjustment of the plates difficult and give rise to overload of the motor serving to effect the adjustment. Moreover, the damper plates, due to their fairly complicated shape, are correspondingly difficult and expensive to fabricate.

SUMMARY OF THE INVENTION It is an object of the present invention to eliminate the disadvantages referred to in the foregoing and according to the invention there is provided a damper unit of the kind referred to above which is characterwhich coinsides with the outer wall while the reminder of said contour is a straight line so that the two ducts surrounding each other through the inner or first part of the housing merge smoothly into two parallel ducts in the outer or last part of the housing, which parallel ducts are separated by a flat partition, said partition having beyond the connection to the tubular patition an aperture of the same shape and size as the total area of a section through the two parallel ducts, the damper having a corresponding shape and size.

When the outer and inner ends of the flow passages through the housing are connected by means of the pipe section or tubular partition referred to above, it becomes possible to utilize a single common damper to control all three flow passages of the unit including the by-pass, which damper may be flat or essentially flat and may have a simple external outline, which results in a substantial simplification of the construction and, thereby, in a more inexpensive fabrication with a minimum of adjustment operations; With the same area of the flow passages, the surface area of the damper is considerably smaller than the total area of the two prior art damper plates referred to above, andthe possible dust deposition on the damper is correspondingly lower. Since the pivot axis of the damper will normally be located in the centre of or, in any event, close to the centre of the damper, there will be no call for any balancing or, at the most, merely a very minor balancing will be called for and, accordingly, a uniform deposition of dust will not produce any incovenient unbalance of the damper. In addition, the risk of the damper becoming jammed against the wall between the two passages in the housing is obviated, which risk is present in the prior art construction in which the damper plates, in one of the extreme positions, overlap the wall in question. In the unit according to the invention, the movement of the damper to or'from one of its two extreme positions will, on the contrary, result in any possible deposits on the damper edge or in the opposed aperture being scraped off.

As mentioned in the foregoing, it is preferred that the partition extends in a median plane through the outermost end of the housing, which offers the additional advantage that the cross-sectional areas of the passages for fresh air and return air becomeequal in case of the normal symmetrical cross-sectional shape of the housing.

According to a further feature of the invention the outermost extremity of the tubular partition or pipe section may be connected directly to the internal surface of the housing and to the innermost terminal edge of the flat partition respectively, whereby it is achieved that, at the point where the pipe section meets the housing or the flat partition, there are no surface on which substantial depositions of dust are able to form.

The section through the two parallel ducts referred to in the foregoing may be a section at right angles to the axial direction of the ducts and, if the ducts are cylindrical, the aperture will in this case be circular and the damper will be shaped accordingly. It is advantageous, however, that the section is oblique and forms an angle to the axialdirection of the ducts which is smaller than 45, by way of preference less than 30.

Since the ventilation system with which the damper unit is associated is normally mounted in such a way that the axial direction of the ducts is vertical, this results in the damper being less liable to collect dust than if it, in one of its extreme positions, were situated approximately at right angles to the axial direction, that is to say horizontally.

Furthermore, when the damper is inclined rather than horizontal in the closing position and vertical in the open position, the travel between the two extreme damper positions is shortened, which is advantageous when the regulation of the damper aperture is effected automatically since a thermally controlled servomotor, as a rule, has only a small movement.

The housing may be divided into two sections in a transversal plane extending essentially through the pivot axis of the damper, which two sections are hingedly connected with each other. A particularly easy access for cleaning and possibly for the removal of the damper is obtained hereby.

BRIEF DESCRIPTION OF THE DRAWINGS Additional characteristic features and advantages of the invention will become apparent from the subsequent description in which reference is made to the accompanying drawings which diagrammatically illustrate an embodiment of a damper unit according to the invention, in which drawings FIG. 1 shows an axial section through the unit in one extreme position of the damper,

FIG. 2 shows a corresponding section in the other extreme position of the damper,

FIG. 3 shows a corresponding section with the damper in an intermediate position,

FIG. 4 is a section corresponding to the one shown in FIG. 1, in which additional features are illustrated which are designed to reduce dust and ice deposits inside the unit, and

FIG. 5 shows a section corresponding to FIG. 1 of a modified embodiment.

DETAILED DESCRIPTION The damper unit shown in the drawings has an elongated tubular housing 1 which may have any crosssectional shape, preferably though circular or regularly polygonal, particularly quadratic. Housing 1 may, for instance, be mounted in the roof ridge of a stable which is to be ventilated by means ofa fan (not shown) which is fitted with two sets of mechanically coupled axial vanes having opposed directions of pitch and located in a central ventilation duct and in a surrounding annular duct, respectively. A blower of this design is shown in the aforesaid Danish patent specification No. I l5,495.

At its upper end housing 1 is terminated with a cover 2 which comprises a tubular portion 3 that forms a continuation of housing I and is connected thereto by means of a hinge 4, and a cover plate 5. Cover plate 5 has an aperture 6 which, in the embodiment shown, extends across half of the cross-sectional area of cover portion 3 and which, towards the centre, is defined by a partition 7 located in the common axial median plane of cover 2 and housing 1. In the upper end of housing 1 there is a partition 8 located in the same plane and the two partitions 7 and 8 have opposing cut-out sections which together define an aperture or by-pass 9 in which a damper I0 is fitted pivotably about a horizontal axis located in said median plane. In the horizontal plane that contains the pivot axis of the damper and which, by way of preference, coincides fully or essentially with the plane in which hinge 4 is situated, there is, secured to the inside of housing I, a narrow annular ledge or shelf 11 which delimits an aperture 12 that is closed by damper when this assumes the horizontal position shown in FIG. 2. There is, however, a certain slight distance between the outer edge of damper 10 and shelf 11 so that, in the closed positon, there will be a certain narrow gap. This entails a certain amount of leakage which, however, is quite insignificant in practice but results in the advantage that the risk of steadily accumulating dust deposits is very substantially reduced. Aperture 9 has the same size and shape as aperture l2 and thus it will be closed by damper 10 when the damper assumes the vertical position shown in FIG.

A pipe section 13 extends obliquely downwards through housing 1 from the bottom edge of partition 8 and the topmost extremity of the pipe section fits tightly to this edge as well as to the inside of that portion of housing 1 which lies vertically below aperture 6. Pipe section 13 is arranged obliquely in such a way that the aperture 14 in the lower end of the section is concentric with the lowermost end of housing 1 and preferably equiform with it. Thus, an annular aperture 15 is defined between the lower endof pipe section 13 and housing 1, and the two apertures 14 and 15 are designed to be connected to the above-mentioned coaxial ducts of the ventilation system (not shown). By way of preference, the areas of the two apertures 14 and 15 are of equal sizes. If, for example, housing 1 has a circular cross-section, the lowermost aperture 14 of pipe section 13 is also circular in cross-section while its topmost aperture 16, just like aperture 6, is semi-circular in cross-section. A pipe section having two thus shaped terminal apertures is developable and can consequently be fabricated from sheet material without difficulty. As touched upon in the foregoing, pipe 1 and, hence, apertures 14 and 15, might alternatively have a polygonal cross-section and, if this is the case, pipe section 13 can be produced either by folding a plate or by joining flat plate portions together.

Inside the vertical duct 17 which connects apertures 6 and 16, there may be mounted a servomotor 18 which, via a linkage 19, is connected to damper l0 and, as indicated in the drawings, motor 18 may be constructed with a sensor portion 20 that projects down into pipe section 13, whereby the position of damper 10 is adjusted in dependence upon the temperature of the return air flowing through the pipe section. Alternatively it is also possible to control motor 17 by a thermostat fitted in the ventilated room itself. Moreover, it is not a condition that the return air flows through the obliquely arranged pipe section since this section could also be connected to that duct in the topmost portion of the housing and the superjacent cover which is designed for taking in fresh air.

In the embodiment illustrated, the fresh air is drawn in underneath the downwardly-curved cover plate 5 and through an aperture 21 in that half of the cover portion 3 which, in FIG. 1, is located to the right-hand side of partition 7. When the damper 10 is in the vertical position shown in FIG. 1, i.e. in one of its end positions, duct 17 and its continuation through pipe section 13 is completely cut off from duct 22 of the unit that connects aperture 21 with the annular aperture 15 in the bottom of housing 1. Thus, all the air injected into the room or rooms by means of the blower is fresh air and the entire volume of return air is exhausted via aperture 6.

In the second end position of damper as illustrated in FIG. 2, the connection between apertures 21 and is closed and, correspondingly, the connection from pipe section 13 to aperture 6 is cut off while the bottom half of aperture 9 in partition 7, 8 is open so that the entire volume of air extracted from the room is returned via duct 22 and aperture 15. In the intermediate position of damper 10 shown in FIG. 3, a part of the room air is recirculated and mixed with a certain amount of fresh air, while a corresponding amount of spent air is exhausted via aperture 6.

As already indicated in FIGS. l-3, it may be expedient to construct damper 10 with a lenticular crosssection so that, in its hollow interior, there will be room for a through supporting shaft that is pivotably journalled in bearings secured to either housing 1 or cover 2. The internal hollow space of the damper can be filled with insulating material or, as shown in FIG. 4, heating elements 23, e.g. electrical heating elements, may be incorporated whose power supply lines can be carried out through or parallel to the damper shaft. It is also possible, as shown in FIG. 4 to mount similar heating elements 24 around the vertical ducts in cover 2 and possibly, around housing 1 as well. FIG. 4 also shows insulating material 25 disposed outside the housing and cover. With the aid of said features it is possible, when employing the damper unit in a cold and humid climate, to substantially reduce ice and/or condensate deposits in the internal ducts as well as on the damper. By reducing the formation of condensate, the danger of dust being deposited on and adhering to the surfaces involved is likewise lessened. It is advantageous, moreover, that the mixing of fresh air and return air in case of complete or partial recirculation takes place closely underneath the intake and discharge apertures since the relatively warm return air hereby limits the cooling effect of the surrounding air upon the damper unit.

The construction illustrated in FIG. 5 closely corresponds to the one shown in FIGS. 1 to 4 and the same reference numerals have been used as in the description of these Figures. The sole difference consists in that damper 10, in the extreme position shown, is not arranged at right angles to the direction of the duct but in an oblique position so that, in said extreme position, it forms an angle to the direction of the axis which, in the embodiment shown, is approximately 45, but which may, with advantage, be less than that.

Consequently, the pivoting movement between the two extreme positions of the damper is reduced and, for this reason, a lower gear ratio is required between the movement produced by servomotor 18 and the movement of the damper than according to FIGS. 1-4, which is indicated by a modified showing oflinkage 19. Likewise, a correspondingly greater adjusting force is obtained hereby.

In addition, in FIG. 5, a cover plate 26 is indicated with dotted lines which covers the upper half of aperture 9 in partition 7, 8. This cover plate is sufficiently staggered in relation to the partition so as not to obstruct the movement of damper 10, but it may also constitute a portion of partition 7, 8 so that only the bottom half of aperture 9 is formed in the partition. If this is the case, damper 10 will have to be journalled or shaped, e.g. cranked, in such a way that its pivoting movement is not impeded.

A consideration of the flow pattern as shown in FIGS.

1-4 with different positions of the damper and of the analogous flow patterns in the embodiment shown in FIG. 5 at different positions of its damper, will show that the top half of aperture 9 serves no useful purpose in the ventilating process. By closing this upper half of the aperture, it is ensured that in the intermediate damper positions no warm and humid air flows from the exhausting duct to the intake duct, so that by closing this top half the risk of condensate formation is obviated which could be the result of the circumstance that it is possible for some of the warm discharge air to be sucked into the intake side through the upper half of the by-pass aperture.

It is also possible to fabricate the damper and/or the housing in their entirety of insulating material, for in stance, plastics material having an interior cell structure with or without incorporated heating elements.

. What we claim is:

1. A damper unit for a ventilation system, comprising:

a. a tubular housing defined by an outer wall and having a first and a second end,

b. a flat partition wall extending longitudinally into said housing from said second end and through a part of the length thereof,

a tubular member extending internally of said housing from said first end towards said second end thereof at an angle with respect to the longitudinal axis of the housing, the end of said tubular member located at said first housing end defining a central aperture substantially coaxial with the outer wall of the housing whereby an annular aperture is formed between said tubular member and said outer wall, the opposite end of said tubular member having a contour comprising a first part which coincides with the inner contour of said outer wall, and a second part which is a straight line contiguous with the inner end of said flat partition wall, whereby first and second through passages are formed within said housing, the first passage connecting said central aperture with the interspace between one side of said partition wall and said outer wall, and the second passage connecting said annular aperture with the interspace between the opposite side of said partition wall and saidouter wall.

d. said flat partition wall having an aperture therein with a contour of the same shape and size as a plane section through said tubular housing, and

e. a damper pivotally supported within said housing on a transverse axis parallel to said flat partition wall and having a contour of the same size and shape as the aperture in said partition wall, whereby said damper may be selectively pivoted between a first end position in which it closes said aperture, and a second end position in which it closes the through passages between said first and second ends of said housing and permits a circulation of air between said central aperture and said surrounding annular aperture located at said first end of said housing.

2. A damper unit as claimed in claim 1, wherein the flat partition extends in a median plane through the second end of the housing.

3. A damper unit as claimed in claim 1, wherein the opposite end of the tubular member connects directly to the internal surface of the housing and to the innermost terminal edge of the flat partition wall.

4. A damper unit as claimed in claim 1, wherein the section through the tubular housing is oblique and forms an angle to the axial direction of the ducts smaller than 45.

5. A damper unit as claimed in claim 1, wherein the housing is divided into two sections by a transverse plane extending essentially through the pivot axis of the damper, said two sections being hingedly connected with each other.

erture located above the damper is substantially closed. =l =l 

1. A damper unit for a ventilation system, comprising: a. a tubular housing defined by an outer wall and having a first and a second end, b. a fLat partition wall extending longitudinally into said housing from said second end and through a part of the length thereof, c. a tubular member extending internally of said housing from said first end towards said second end thereof at an angle with respect to the longitudinal axis of the housing, the end of said tubular member located at said first housing end defining a central aperture substantially coaxial with the outer wall of the housing whereby an annular aperture is formed between said tubular member and said outer wall, the opposite end of said tubular member having a contour comprising a first part which coincides with the inner contour of said outer wall, and a second part which is a straight line contiguous with the inner end of said flat partition wall, whereby first and second through passages are formed within said housing, the first passage connecting said central aperture with the interspace between one side of said partition wall and said outer wall, and the second passage connecting said annular aperture with the interspace between the opposite side of said partition wall and said outer wall. d. said flat partition wall having an aperture therein with a contour of the same shape and size as a plane section through said tubular housing, and e. a damper pivotally supported within said housing on a transverse axis parallel to said flat partition wall and having a contour of the same size and shape as the aperture in said partition wall, whereby said damper may be selectively pivoted between a first end position in which it closes said aperture, and a second end position in which it closes the through passages between said first and second ends of said housing and permits a circulation of air between said central aperture and said surrounding annular aperture located at said first end of said housing.
 2. A damper unit as claimed in claim 1, wherein the flat partition extends in a median plane through the second end of the housing.
 3. A damper unit as claimed in claim 1, wherein the opposite end of the tubular member connects directly to the internal surface of the housing and to the innermost terminal edge of the flat partition wall.
 4. A damper unit as claimed in claim 1, wherein the section through the tubular housing is oblique and forms an angle to the axial direction of the ducts smaller than 45*.
 5. A damper unit as claimed in claim 1, wherein the housing is divided into two sections by a transverse plane extending essentially through the pivot axis of the damper, said two sections being hingedly connected with each other.
 6. A damper unit as claimed in claim 1, wherein the housing has a narrow circumferential ledge in a transverse plane which contains the pivot axis of the damper, which limits the flow passage apertures controlled by the damper.
 7. A damper unit as claimed in claim 1 wherein heating elements are incorporated into the damper and the adjoining portion of the outer wall of the housing.
 8. A damper unit as claimed in claim 1 adapted to be mounted vertically, and wherein the portion of the aperture located above the damper is substantially closed. 